AP Bio Unit 1-5

What are enzymes?

Specialized proteins that act as biological catalysts, speeding up reactions without being consumed.

How do enzymes lower activation energy?

By stabilizing the transition state and bringing substrates close together for reactions.

What determines enzyme specificity?

The unique shape and charge of the enzyme’s active site.

What forms when a substrate binds to an enzyme?

An enzyme substrate complex.

What are the two models of enzyme interaction?

Lock and Key (exact fit) and Induced Fit (active site adjusts shape).

Why is tertiary structure important for enzymes?

It creates the active site; even small amino acid changes can destroy function.

What is the optimal temperature for human enzymes?

Around 37°C.

What happens when enzymes denature?

Their structure unravels, and the active site no longer fits the substrate.

How does pH affect enzyme activity?

Each enzyme has an optimal pH; deviations disrupt bonds and alter shape.

What do inhibitors and activators do?

Inhibitors reduce enzyme activity; activators increase it.

What do living systems require to maintain organization?

A constant influx of energy.

What does the second law of thermodynamics state?

Energy transfers increase entropy (disorder).

Why must energy input exceed energy output?

To maintain homeostasis and survival.

What are coupled reactions?

Exergonic (energy releasing) reactions power endergonic (energy requiring) ones using ATP.

What is the photosynthesis equation?

6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Where does photosynthesis occur?

In chloroplasts.

What happens in light dependent reactions?

Light splits water, releasing O2 and producing ATP + NADPH (in thylakoids)

What happens in the Calvin Cycle?

ATP + NADPH convert CO₂ into glucose (in the stroma).

Why is photosynthesis essential?

It provides chemical energy and oxygen for ecosystems.

What is the cellular respiration equation?

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

What is the main goal of respiration?

To produce ATP.

Where does glycolysis occur and what does it do?

In the cytoplasm; splits glucose into pyruvate, producing 2 ATP (no oxygen required).

What happens in the Krebs Cycle?

Produces CO₂, ATP, NADH, and FADH₂ (in the mitochondrial matrix).

What happens in the Electron Transport Chain (ETC)?

Uses NADH and FADH₂ to power ATP synthase for mass ATP production (in inner membrane).

What is fermentation?

Anaerobic ATP production (less efficient); includes lactic acid and alcoholic types.

What is cell homeostasis?

The maintenance of a stable internal environment.

What is the role of the cell membrane in homeostasis?

It selectively regulates molecule movement.

What is passive transport?

Movement down the gradient without ATP (e.g., diffusion, facilitated diffusion).

What is active transport?

Movement against the gradient using ATP (e.g., sodium potassium pump).

What is osmoregulation?

Water balance control using aquaporins.

How do cells regulate nutrient intake?

Via specific transport proteins (e.g., GLUT4 for glucose).

What helps protect enzymes under heat stress?

Heat shock proteins.

What do negative feedback loops do?

Restore conditions to normal (e.g., insulin lowers blood sugar).

What do positive feedback loops do?

Amplify a response (e.g., calcium release in muscle contraction).

What are the fundamental units of life?

Cells.

What are the two main types of cells?

Prokaryotic and eukaryotic.

Do prokaryotic cells have a nucleus?

No; they lack a membrane bound nucleus.

Do eukaryotic cells have organelles?

Yes; they contain membrane bound organelles.

Example of a prokaryote?

Bacteria.

Example of a eukaryote?

Plants and animals.

Why are cells small?

Small cells have a higher surface area to volume ratio for efficient exchange.

What happens when a cell grows too large?

Material exchange becomes less efficient.

How do eukaryotic cells deal with large size?

By compartmentalization and specialized shapes.

What does the Endosymbiotic Theory explain?

How mitochondria and chloroplasts evolved from prokaryotes.

What evidence supports it?

Circular DNA, prokaryote like ribosomes, and double membranes.

Mitochondria resemble what?

Ancient aerobic bacteria.

Chloroplasts resemble what?

Cyanobacteria.

What is the plasma membrane made of?

A phospholipid bilayer.

What is the fluid mosaic model?

A dynamic membrane of moving phospholipids and proteins.

Which parts of phospholipids are polar and nonpolar?

Heads = hydrophilic; tails = hydrophobic.

What do embedded proteins do?

Transport, signaling, support, and enzymatic activity.

What does cholesterol do in membranes?

Regulates fluidity.

What do glycoproteins and glycolipids do?

Help in cell recognition and communication.

What molecules pass freely through the membrane?

Small, nonpolar molecules (O₂, CO₂).

What molecules need transport proteins?

Large polar molecules and ions.

What helps water move faster across membranes?

Aquaporins.

Does passive transport need energy?

No, it moves down the concentration gradient.

What is simple diffusion?

Molecules moving directly through the bilayer.

What is facilitated diffusion?

Molecules moving through channel or carrier proteins.

What is osmosis?

Diffusion of water across a membrane.

What is osmosis driven by?

Water potential differences.

What happens in a hypotonic solution?

Water enters; animal cells may burst, plant cells become turgid.

What happens in a hypertonic solution?

Water exits; animal cells shrink, plant cells plasmolyze.

What happens in an isotonic solution?

No net water movement; animal cells stay normal.

Does active transport require energy?

Yes, usually ATP.

What does the sodium potassium pump do?

Pumps Na⁺ out and K⁺ in, maintaining gradients.

What is secondary active transport?

Uses one molecule’s gradient to move another against its gradient.

What is endocytosis?

Cell takes in materials by forming vesicles.

What is phagocytosis?

Cell “eating” large particles.

What is pinocytosis?

Cell “drinking” extracellular fluid.

What is receptor mediated endocytosis?

Selective uptake of specific molecules via receptors.

What is exocytosis?

Vesicles release materials outside the cell.

What does compartmentalization do in eukaryotes?

Increases metabolic efficiency.

What does the mitochondrion do?

Produces ATP through cellular respiration.

What do chloroplasts do?

Perform photosynthesis in plants and algae.

What does the rough ER do?

Synthesizes and folds proteins.

What does the smooth ER do?

Synthesizes lipids and detoxifies.

What does the Golgi apparatus do?

Modifies, packages, and ships proteins and lipids.

What do lysosomes do?

Break down macromolecules and old organelles.

What do vacuoles do?

Store materials and maintain plant turgor pressure.

What do ribosomes do?

Build proteins from mRNA instructions.

How are the ER, Golgi, and vesicles connected?

Proteins made in the ER → modified in the Golgi → exported via vesicles.

What are macromolecules made of?

Smaller subunits called monomers.

What forms when many monomers link together?

A polymer.

What are the four major macromolecules?

Carbohydrates, proteins, lipids, and nucleic acids.

What bond connects monomers?

Covalent bond.

What is dehydration synthesis?

Joining monomers by removing water to form polymers.

What is hydrolysis?

Breaking polymers into monomers using water.

What are the main elements in macromolecules?

Carbon, hydrogen, oxygen, nitrogen, and phosphorus.

Monomer and bond of nucleic acids?

Nucleotide; phosphodiester bond.

Monomer and bond of proteins?

Amino acid; peptide bond.

Monomer and bond of carbohydrates?

Monosaccharide; glycosidic linkage.

Monomer and bond of lipids?

Fatty acids + glycerol; ester bond.

What are the three parts of a nucleotide?

Sugar, phosphate group, nitrogenous base.

What are DNA’s bases?

A, T, G, C (A pairs with T; G pairs with C).

What are RNA’s bases?

A, U, G, C (U replaces T).

What sugar does DNA have?

Deoxyribose (no OH at 2' carbon).

What sugar does RNA have?

Ribose (has OH at 2' carbon).

What is DNA’s structure?

Double helix, antiparallel strands (5'→3' and 3'→5').

What is RNA’s structure?

Single stranded and more reactive.